1. Field of the Invention
This invention relates to a light weight, sealing cover, or lid, which is suitable for the packaging of semiconductor devices; more particularly to a light weight lid which has a high thermal conductivity and is also electrically conductive.
2. Description of the Prior Art
The use of ceramic packages for semiconductor devices is well known. Typically, such a package includes a ceramic substrate to which a lid must be sealed after the semiconductor device is placed therein. Lids of the type used in connection with packages for semiconductor devices are generally of metallic or ceramic materials. Metal lids are often formed of an iron base material such as "Kovar", Alloy 42, Alloy 45 and Alloy 46. The metal lid is usually electroplated with a base coating of nickel or some other metal and a final coating of pure gold is then applied. The gold overlayer provides an oxide-free surface suitable for bonding. This type of lid is often sealed using a preformed solder frame that is placed between the lid and the package housing and then the lid and package is sealed by reflowing the solder preform.
In addition to metal lids, it has also been proposed to use ceramic lid assemblies for hermetic sealing of semiconductor packages. Such ceramic lids may be provided with a heat fusible layer around a periphery for hermetic sealing or a non hermetic seal using epoxy, cyanate ester, silicone or any other suitable organic adhesive. Ceramic materials which are used include oxides and nitrides of aluminum, and oxides of beryllium and magnesium. Where ceramic lid assemblies are employed, preform solder frames may not be necessary to accomplish bonding.